US3876461A - Semiconductor process - Google Patents

Semiconductor process Download PDF

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Publication number
US3876461A
US3876461A US394228A US39422873A US3876461A US 3876461 A US3876461 A US 3876461A US 394228 A US394228 A US 394228A US 39422873 A US39422873 A US 39422873A US 3876461 A US3876461 A US 3876461A
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Prior art keywords
plastic
methyl
pyrollidone
semiconductor
minutes
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Expired - Lifetime
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US394228A
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Dervin L Flowers
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Motorola Solutions Inc
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Motorola Inc
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/50—Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
    • H01L21/56—Encapsulations, e.g. encapsulation layers, coatings
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
    • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
    • C08G59/44—Amides
    • C08G59/448—Lactames
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S156/00—Adhesive bonding and miscellaneous chemical manufacture
    • Y10S156/918—Delaminating processes adapted for specified product, e.g. delaminating medical specimen slide
    • Y10S156/93—Semiconductive product delaminating, e.g. delaminating emiconductive wafer from underlayer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T156/00—Adhesive bonding and miscellaneous chemical manufacture
    • Y10T156/11—Methods of delaminating, per se; i.e., separating at bonding face
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49117—Conductor or circuit manufacturing
    • Y10T29/49121—Beam lead frame or beam lead device

Definitions

  • the semiconductor chip or die is mounted on a lead frame.
  • the lead frame has a support pad forthe die and a plurality of fingers which provide the electrical terminals for the device.
  • the lead fraineandthe semiconductor chip is encapsulated in a molded plastic package.
  • the tie bar portions of the lead frame are then removed to form separated electrical terminals for the finished de vice.
  • Residues or flash from the encapsulation pro cess may coat the electrical terminals, the heat from the encapsulation may oxidize the leads or other contaminants from the encapsulation process may so coat the terminals as to destroy electric continuity to the semiconductor device therein and/or may not permit the package to be reliably soldered into a circuit.
  • Various steps have been utilized to overcome this problem, one of the most common being a mechanical sandblast of the device.
  • certain chromic acid or dimethyl formamide solvents have been suggested.
  • a problem encountered with most solvent type processes is that the solvent in cleaning up the parts also attacks the material from which the package is formed leading to either defective packages or at least packages which appear defective from a cosmetic standpoint.
  • a further object of the invention is to provide an improved process for cleaning and improving the plating and hence solderability of the leads for semiconductor devices.
  • N-methyl-2-pyrollidone is a highly polar aprotic liquid which is widely employed as a chemical reaction medium.
  • M-PYROL N-methyl-Z-pyrollidone Handbook published by GAF Corporation (1972). Its various physical property data is set forth therein.
  • an improved method for the manufacture of plastic encapsulated semiconductor devices which includes the step of immersing an encapsulated semiconductor device in N-methyl-Z-pyrollidone for l to 20 minutes at a temperature between 70 and l 10C. Following immersion the semiconductors are rinsed with water to remove the excess. The parts appear to be coated with an absorbed monolayer of the Nmethyl-2-pyrollidone, while removing contaminants during the immersion process.
  • the solution may contain a surfactant such as a sulfosuccinate ester.
  • a semiconductor chip or die is mounted on a lead frame.
  • the lead frame has a support pad for the die and a plurality of fingers which provide the electrical terminals for the device.
  • the lead frame and the semiconductor "chip is encapsulatedin ;a molded plastic package.
  • the molding of plastic semiconductor devices can result in excess flashtha't isdifficult to remove.
  • the result is that the parts may be tested as open circuits'because of a thin film on the leads.
  • plating and solder rejects can be common since the film of flash will not accept the plating material.
  • Mechanical deflashing such as the use of polycarbonate particles in a sand blaster will remove the flash between the leads but not always the thin film flash on the leads.
  • the use of sand in a sandblaster may remove the thin film but the mechanical damage to the leads that results can seriously perturb both reliability and appearance of the semiconductor devices.
  • the improved solderability of the devices following the N-methyl-Z-pyrollidone treatment is but one of the advantages of the treatment. While the exact reason is not clear results from testing have shown improved reliability of devices treated, perhaps because of absorbed N-methyI-Z-pyrollidone in the plastic whether the plastic is phenolic, epoxy, or silicone. Thus while the N-methyl-Z-pyrollidone does not attack the plastic it appears to be absorbed into the surface leading to higher reliability.
  • a group of epoxy encapsulated integrated circuits having been immersed in the methylpyrollidone for 5 minutes at 80C were TI-IB (Temperature-Humidity-Bias) tested at 80C with percent humidity while another group of untreated devices of the same type were tested under the same conditions. The untreated group reached a percent failure rate in 30 hours while the 10 percent failure rate for the N-methyl-Z-pyrollidone treated group took l 10 hours to reach the 10 percent failure rate.
  • plastic is selected from the group consisting of phenolics, silicones and epoxies.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Physics & Mathematics (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Encapsulation Of And Coatings For Semiconductor Or Solid State Devices (AREA)

Abstract

A process for improving the reliability and solderability characteristics of plastic encapsulated semiconductor devices which includes the step of immersing the devices in N-methyl-2pyrollidone.

Description

United States Patent 11 1 1111 3,876,461 Flowers Apr. 8, 1975 SEMICONDUCTOR PROCESS 3.698.940 10/1972 Merscreau 117/213 1 inventor: Deni Flowers, Scottsdale. Ariz- 33331333? 511333 1111112111111:::::::::::.......::::::..11413.? [73] Assignee: Motorola, Inc., Chicago. 111.
[22] Filed: Sept. 4, 1973 Primary E.\'aminer-Michae1 F1 Esposito [211 App]. No: 394,228 411315121, Agent, or F1rm-V1ncent .1. Rauner; Henry [52] U.S. Cl. 117/213; l1-7/47 A; 117/113; 117/201; 117/227 [51] Int. Cl B44d 1/20; B44d 1/092 [57] ABSTRACT [58] held of Search 1717/20] 1 47 A process for improving the reliability and solderabil- 1 l 13; 357/72? 29/588 ity characteristics of plastic encapsulated semiconductor devices which includes the step of immersing the [56] Refere'lces C'ted devices in N-methyI-Z-pyrollidone.
UNITED STATES PATENTS 3,619,243 1 H1971 Brindisi.. 1 17/47 A 4 Claims, No Drawings BACKoIiouND QFiTl-Ili iINl/ENTI'ON This invention relatesto' 'the manufacture of semiconductor devices and more particularly to the manufacture of plastic encapsulated semiconductor devices.
In a conventional method of manufacturing semiconductor devices", and particularly integrated circuits, the semiconductor chip or die is mounted on a lead frame. The lead frame has a support pad forthe die and a plurality of fingers which provide the electrical terminals for the device. Following suitable bonding "between portions of the semiconductor device and the fingers of the lead frame, the lead fraineandthe semiconductor chip is encapsulated in a molded plastic package. The tie bar portions of the lead frame are then removed to form separated electrical terminals for the finished de vice. Residues or flash from the encapsulation pro cess may coat the electrical terminals, the heat from the encapsulation may oxidize the leads or other contaminants from the encapsulation process may so coat the terminals as to destroy electric continuity to the semiconductor device therein and/or may not permit the package to be reliably soldered into a circuit. Various steps have been utilized to overcome this problem, one of the most common being a mechanical sandblast of the device. Also certain chromic acid or dimethyl formamide solvents have been suggested. However, a problem encountered with most solvent type processes is that the solvent in cleaning up the parts also attacks the material from which the package is formed leading to either defective packages or at least packages which appear defective from a cosmetic standpoint.
It is therefore an object of this invention to provide an improved semiconductor process for the flash removal of plastic encapsulated devices.
A further object of the invention is to provide an improved process for cleaning and improving the plating and hence solderability of the leads for semiconductor devices.
N-methyl-2-pyrollidone is a highly polar aprotic liquid which is widely employed as a chemical reaction medium. A listing of its many suggested uses is found in M-PYROL (N-methyl-Z-pyrollidone) Handbook published by GAF Corporation (1972). Its various physical property data is set forth therein.
It is a further object of this invention to provide an improved process for the manufacture of semiconductor devices utilizing N-methyl-Z-pyrollidone.
SUMMARY OF THE INVENTION In accordance with the invention there is provided an improved method for the manufacture of plastic encapsulated semiconductor devices which includes the step of immersing an encapsulated semiconductor device in N-methyl-Z-pyrollidone for l to 20 minutes at a temperature between 70 and l 10C. Following immersion the semiconductors are rinsed with water to remove the excess. The parts appear to be coated with an absorbed monolayer of the Nmethyl-2-pyrollidone, while removing contaminants during the immersion process. The solution may contain a surfactant such as a sulfosuccinate ester.
Further objects and advantages will be noted in the following complete description thereof of the preferred process in accordance with the invention.
COMPLETE DESCRIPTION As in a conventional method of manufacturing semiconductor devicesyand particularly integrated circuits, a semiconductor chip or die is mounted on a lead frame. The lead frame has a support pad for the die and a plurality of fingers which provide the electrical terminals for the device. Following forming of suitable bonding wires'between portions of the semiconductor device and'the fingers'of the lead-frame, the lead frame and the semiconductor "chip is encapsulatedin ;a molded plastic package. 3 i
The molding of plastic semiconductor devices can result in excess flashtha't isdifficult to remove. The result is that the parts may be tested as open circuits'because ofa thin film on the leads. Also plating and solder rejects can be common since the film of flash will not accept the plating material. Mechanical deflashing such as the use of polycarbonate particles in a sand blaster will remove the flash between the leads but not always the thin film flash on the leads. The use of sand in a sandblaster may remove the thin film but the mechanical damage to the leads that results can seriously perturb both reliability and appearance of the semiconductor devices. Various chemical strippers have been tried with a certain amount of success but such strippers, for example, chromic acid, phenol-dichlorobenzene or dimethyl formamide can be absorbed into the plastic putting alkali, halogen, or acidic contamination into the plastic matrix.
The foregoing problems have been discovered to be largely overcome by immersion of encapsulated transistor packages immediately after molding in N-methyl- 2-pyrollidone for .1 to 20 minutes. The N-methyl-Z- pyrollidone is non-corrosive and non-toxic with a high polarity (Dipole Moment of 4.09D). The solution apparently functions by destroying on thin film only the chemisorption bonds between the metal and the plastic flash thus lifting the flash from the metal leads rather than dissolving the flash. Obviously a solution which operated by dissolving the flash would also begin to attack the packaging material. Following the immersion in the methyl pryollidone bath, held at a temperature of approximately 100C for 5 minutes, the parts are rinsed in water at a temperature of to C for 15 to 20 seconds. Following this treatment devices which required hand removal of flash was less than 5/10 of 1 percent which is in the order of magnitude better than previous experience with the mechanical deflashing.
Addition of 0.5 percent of a dioctyl-sulfosuccinate permits the time of immersion to be reduced to 2 minutes and the temperature of the bath to 80C.
The improved solderability of the devices following the N-methyl-Z-pyrollidone treatment is but one of the advantages of the treatment. While the exact reason is not clear results from testing have shown improved reliability of devices treated, perhaps because of absorbed N-methyI-Z-pyrollidone in the plastic whether the plastic is phenolic, epoxy, or silicone. Thus while the N-methyl-Z-pyrollidone does not attack the plastic it appears to be absorbed into the surface leading to higher reliability. A group of epoxy encapsulated integrated circuits having been immersed in the methylpyrollidone for 5 minutes at 80C were TI-IB (Temperature-Humidity-Bias) tested at 80C with percent humidity while another group of untreated devices of the same type were tested under the same conditions. The untreated group reached a percent failure rate in 30 hours while the 10 percent failure rate for the N-methyl-Z-pyrollidone treated group took l 10 hours to reach the 10 percent failure rate.
In another group of phenolic encapsulated integrated circuits the untreated group reached a 10 percent fail- 1. In a process of manufacturing a semiconductor device wherein a semiconductor chip is mounted on a lead frame and a plastic encapsulation is molded therearound, the improvement comprising the step of:
immersing the device in a solution of N-methyl-Z- pyrollidone heated to -l10C for a period of l-2O minutes.
2. A process as recited in claim 1 wherein the plastic is selected from the group consisting of phenolics, silicones and epoxies.
3. A process as recited in claim 2 wherein the immersion time is 5 minutes.
4. A process as recited in claim 1 wherein said solution also contains a surfactant.

Claims (4)

1. IN A PROCESS OF MANUFACTURING A SEMICONDUCTOR DEVICE WHEREIN A SEMICONDUCTOR CHIP IS MOUNTED ON A LEAD FRAME AND A PLASTIC ENCAPSULATION IS MOLDED THEREAROUND, THE IMPROVEMENT COMPRISING THE STEP OF: IMMERSING THE DEVICE IN A SOLUTION OF N-METHYL-2PYROLLIDONE HEATED TO 70*-110*C FOR A PERIOD OF 1-20 MINUTES.
2. A process as recited in claim 1 wherein the plastic is selected from the
3. A process as recited in claim 2 wherein the immersion time is 5 minutes.
4. A process as recited in claim 1 wherein said solution also contains a surfactant.
US394228A 1973-09-04 1973-09-04 Semiconductor process Expired - Lifetime US3876461A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0021149A1 (en) * 1979-06-26 1981-01-07 International Business Machines Corporation Cleaning composition, process for its production and its use
US4784872A (en) * 1984-11-17 1988-11-15 Messerschmitt-Boelkow-Blohm Gmbh Process for encapsulating microelectronic semi-conductor and layer type circuits
US4882298A (en) * 1987-07-30 1989-11-21 Messerschmitt-Boelkow-Blohm Gmbh Method for encapsulating microelectronic semiconductor and thin film devices

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3619243A (en) * 1970-02-17 1971-11-09 Enthone No rerack metal plating of electrically nonconductive articles
US3698940A (en) * 1970-01-26 1972-10-17 Macdermid Inc Method of making additive printed circuit boards and product thereof
US3791986A (en) * 1971-10-28 1974-02-12 Enthone Preconditioner concentrate
US3808028A (en) * 1971-08-11 1974-04-30 Western Electric Co Method of improving adhesive properties of a surface comprising a cured epoxy

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3698940A (en) * 1970-01-26 1972-10-17 Macdermid Inc Method of making additive printed circuit boards and product thereof
US3619243A (en) * 1970-02-17 1971-11-09 Enthone No rerack metal plating of electrically nonconductive articles
US3808028A (en) * 1971-08-11 1974-04-30 Western Electric Co Method of improving adhesive properties of a surface comprising a cured epoxy
US3791986A (en) * 1971-10-28 1974-02-12 Enthone Preconditioner concentrate

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0021149A1 (en) * 1979-06-26 1981-01-07 International Business Machines Corporation Cleaning composition, process for its production and its use
US4276186A (en) * 1979-06-26 1981-06-30 International Business Machines Corporation Cleaning composition and use thereof
US4784872A (en) * 1984-11-17 1988-11-15 Messerschmitt-Boelkow-Blohm Gmbh Process for encapsulating microelectronic semi-conductor and layer type circuits
US4882298A (en) * 1987-07-30 1989-11-21 Messerschmitt-Boelkow-Blohm Gmbh Method for encapsulating microelectronic semiconductor and thin film devices

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